OCR A Jun 2012 Paper 5 Q4

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4 Nitrogen dioxide reacts with ozone as shown below. 2NO2(g) + O3(g) N2O5(g) + O2(g) (a) The kinetics of the reaction between NO2 and O3 was investigated and the following experimental results were obtained. experiment [NO2(g)] / mol dm3 [O3(g)] / mol dm3 initial rate / mol dm3 s1 0.00150 0.00225 0.00225 0.00250 0.00250 0.00500 4.80108 7.20108 1.44107 (i) Determine the rate equation and rate constant for the reaction of NO2(g) and O3(g). In your answer you should make clear how your conclusions fit with the experimental results.[8]OCR 2012<br />
 (ii) Suggest a possible two-step mechanism for this reaction.[2] (b) The feasibility of the reaction between NO2 and O3 is influenced by the enthalpy change and entropy change of the reaction and the temperature. 2NO2(g) + O3(g) N2O5(g) + O2(g) H = 198 kJ mol1 S = 168 J K1 mol1 (i) Explain why this reaction has a negative entropy change.[2] (ii) Calculate the value of G, in kJ mol1, at 25 C for the reaction of NO2 with O3. (iii) State and explain how the feasibility of this reaction will change with increasing temperature. G =kJ mol1 [3][2]OCR 2012 [Total: 17] Turn over<br />

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